Pump chamber position indicator

ABSTRACT

A pump with a position indicator is disclosed. The pump includes a pump housing, wherein the pump housing includes a flexible bladder disposed therein; a first fluid zone, wherein the first fluid zone is operable to allow flow of a first fluid into and out of the first fluid zone; and a second fluid zone, wherein the second fluid zone is operable to allow flow of a second fluid into and out of the second fluid zone. The pump further includes a flexible position indicator disposed in the first fluid zone and in communication with the flexible bladder, wherein the flexible position indicator is operable to detect a linear position of the flexible bladder, and wherein the flexible bladder fluidly isolates the first fluid zone from the second fluid zone.

PRIORITY CLAIM

The present application is a non-provisional application of and claims the benefit of and priority to U.S. Prov. App. Ser. No. 62/203,779, filed Aug. 11, 2015, the entire disclosure of which is hereby expressly incorporated herein by reference.

BACKGROUND

In subsea drilling operations, equipment on the seabed is connected to a platform or vessel via a drilling riser. The riser typically provides a return path for drilling mud that has been used in drilling operations to return the mud to the vessel or platform. Oftentimes, the mud returning through the riser can have a density greater than that of the ambient seawater, so that the pressure exerted on a formation in the seabed by the column of mud in the riser is greater than that exerted by seawater in the absence of the riser.

One way to deal with problems associated with increased pressure on a formation from high density drilling mud is the use of dual gradient drilling. In dual gradient drilling, a pump can be placed on the seabed, and can be powered, for example, by a seawater powered turbine. The pump serves to isolate the well from the hydrostatic pressure of the mud by directing the mud through a separate return line, thereby allowing replacement of the mud in the riser with seawater.

In order for the pump to function properly, however, an operator must be able to determine the position of pump components, such as, for example, a flexible pump bladder within the pump housing. With this knowledge, the operator can then control the pump, or a series of pumps, to help control pressure in the well. In known pumps, the position of such components is typically measured using an indicator rod, the structure of which is described in greater detail as follows herein.

SUMMARY

Disclosed herein is a pump with a position indicator. The pump includes a pump housing, wherein the pump housing includes a flexible bladder disposed therein; a first fluid zone, wherein the first fluid zone is operable to allow flow of a first fluid into and out of the first fluid zone; and a second fluid zone, wherein the second fluid zone is operable to allow flow of a second fluid into and out of the second fluid zone. The pump further includes a flexible position indicator disposed in the first fluid zone and in communication with the flexible bladder, wherein the flexible position indicator is operable to detect a linear position of the flexible bladder, and wherein the flexible bladder fluidly isolates the first fluid zone from the second fluid zone.

Additionally disclosed herein is a dual gradient drilling system for subsea operations. The drilling system includes a water supply line comprising a water supply line inlet and a water supply line outlet; a manifold inlet, the manifold inlet in fluid communication with the water supply line; and a mud return line comprising a mud return line inlet and a mud return line outlet. The system further includes a mud lead line, the mud lead line in fluid communication with the mud return line; a pump housing, wherein the pump housing includes a flexible bladder disposed therein, wherein the flexible bladder fluidly isolates the manifold inlet from the mud lead line; and a flexible position indicator disposed proximate the manifold inlet and in communication with the flexible bladder, wherein the flexible position indicator is operable to detect a linear position of the flexible bladder within the pump housing.

Further disclosed herein is a method for detecting displacement of a displaceable component in a pump housing. The method includes the steps of disposing a flexible position indicator proximate the pump housing and in communication with the displaceable component in the pump housing, the displaceable component operable to be displaced by fluid movement in the pump housing; allowing the flexible position indicator to be displaced responsive to movement of the displaceable component in the pump housing; detecting a displacement of the flexible position indicator; and monitoring a position of the displaceable component in the pump housing.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following descriptions, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the disclosure and are therefore not to be considered limiting of the disclosure's scope as it can admit to other equally effective embodiments.

FIG. 1 is a schematic diagram of a mud pump.

FIG. 2 is a schematic diagram of a mud pump depicting the pressurizing of mud within a mud space.

FIG. 3 is a schematic diagram of a mud pump of the present disclosure.

FIG. 4 is a graphic illustration of a position indicator with a transducer cable.

FIG. 5 is an enlarged view of a ferrule connector from FIG. 4.

DETAILED DESCRIPTION

A schematic diagram of a mud pump is shown in FIGS. 1 and 2. FIG. 1 includes a side sectional view of an example of a pump 10 for use with a lift pump assembly (not shown). Pump 10 includes a generally hollow pump housing 12. An embodiment of a flexible bladder 14 is shown within the housing 12, which partitions the space within the housing 12 to define a mud space 16 on one side of the flexible bladder 14, and a water space 18 on an opposing side of flexible bladder 14. Flexible bladder 14 provides a fluidly-sealing barrier between mud space 16 and water space 18.

In the example of FIG. 1, flexible bladder 14 has a generally elliptical shape and an upper open space 20 formed through a side wall. Upper open space 20 is shown coaxially registered with an opening 22 formed through a side wall of pump housing 12. A disk-like cap 24 bolts onto opening 22, where cap 24 has an axially downward depending lip 26 that coaxially inserts within opening 22 and upper open space 20. A portion of the flexible bladder 14 adjacent its upper open space 20 is wedged between lip 26 and opening 22 to form a sealing surface between flexible bladder 14 and pump housing 12.

A lower open space 28 is formed on a lower end of flexible bladder 14 distal from upper open space 20, which in the example of FIG. 1 is coaxial with upper open space 20. An elliptical bumper 30 is shown coaxially set in the lower open space 28. The bumper 30 includes upper and lower segments 32, 34, which are coupled together in a clamshell like arrangement, and respectively seal against upper and lower radial surfaces on the lower open space 28. The combination of sealing engagement of cap 24 and bumper 30 with upper and lower open spaces 20, 28 of flexible bladder 14, effectively define a flow barrier across the opposing surfaces of flexible bladder 14.

Further shown in the example of FIG. 1 is an axial rod 36 that attaches coaxially to upper segment 32 and extends axially away from lower segment 34 and through opening 22. The rod 36 acts as a position indicator which, according to its axial position within the housing 12, can indicate the position of the flexible bladder 14 within the housing 12.

Still referring to FIG. 1, a mud return line 38 is shown having an inlet end 40 and an outlet end 42. A mud inlet valve 44 in mud return line 38 provides selective fluid communication from inlet end 40 to a mud lead line 46 shown branching from mud return line 38. Lead line 46 attaches to an annular connector 48, which in the illustrated example is bolted onto housing 12. Connector 48 mounts coaxially over an opening 50 shown formed through a sidewall of housing 12 and allows communication between mud space 16 and mud return line 38 through lead line 46. A mud exit valve 52 is shown in mud return line 38 and provides selective communication between mud return line 38 and outlet end 42.

Water may be selectively delivered into water space 18 via a water supply line 54. A water inlet lead line 56 has an end coupled with water supply line 54 and an opposing end attached with a manifold assembly 58 that mounts onto cap 24. The embodiment of the manifold assembly 58 of FIG. 1 includes a connector 60 mounted onto a free end of a tubular manifold inlet 62, an annular body 64, and a tubular manifold outlet 66, where the inlet and outlet 62, 66 mount on opposing lateral sides of the body 64 and are in fluid communication with body 64.

Connector 60 provides a connection point for an end of water inlet lead line 56 to manifold inlet 62, so that lead line 56 is in fluid communication with body 64. A lower end of manifold body 64 couples onto cap 24, and the annulus of the manifold body 64 is in fluid communication with water space 18 through a hole in the cap 24 that registers with opening 22. An outlet connector 68 is provided on an end of manifold outlet 66 distal from manifold body 64, which has an end opposite its connection to manifold outlet 66 that is attached to a water outlet lead line 70. On an end opposite from connector 68, water outlet lead line 70 attaches to a water discharge line 72.

A water inlet valve 74 shown in water inlet lead line 56 provides selective water communication from a vessel (not shown) to water space 18 via water inlet lead line 56 and manifold assembly 58. A water outlet valve 76 shown in water outlet lead line 70 selectively provides communication between water space 18 and water discharge line 72 through manifold assembly 58 and water outlet lead line 70.

In one example of operation of pump 10 of FIG. 1, mud inlet valve 44 is in an open configuration, so that mud in mud return line 38 communicates into mud return line 38 and mud lead line 46 as indicated by arrow A_(Mi). Further in this example, mud exit valve 52 is in a closed position thereby diverting mud flow into connector 48, through opening 50, and into mud space 16. As illustrated by arrow A_(U), flexible bladder 14 is urged in a direction away from opening 50 by the influx of mud, thereby imparting a force against water within water space 18. In the example, water outlet valve 76 is in an open position, so that water forced from water space 18 by flexible bladder 14 can flow through manifold body 64 and manifold outlet 66 as illustrated by arrow A_(Wo). After exiting manifold outlet 66, water is routed through water outlet lead line 70 and into water discharge line 72.

An example of pressurizing mud within mud space 16 is illustrated in FIG. 2, wherein valves 44, 76 are in a closed position and valves 74, 52 are in an open position. In this example, pressurized water from water supply line 54 is free to enter manifold assembly 58, where as illustrated by arrow A_(Wi), the water is diverted through opening 22 and into water space 18. Introducing pressurized water into water space 18 urges flexible bladder 14 in a direction shown by arrow A_(D). Pressurized water in the water space 18 urges flexible bladder 14 against the mud, which pressurizes mud in mud space 16 and directs it through opening 50. After exiting opening 50, the pressurized mud flows into lead line 46, where it is diverted to mud return line 38 through open mud exit valve 52 as illustrated by arrow A_(Mo). Thus, providing water at a designated pressure into water supply line 54 can sufficiently pressurize mud within mud return line 38 to force mud to flow back to a vessel (not shown).

As discussed above, and shown in FIGS. 1 and 2, axial rod 36 attaches to upper segment 32 of the bumper 30, which is in turn attached to the lower open space 28 of the flexible bladder 14. One purpose of the rod 36 is to act as a position indicator, which indicates the position of the flexible bladder 14 within the housing 12. One problem associated with the rod 36, however, is that operation of the pump 10 requires the rod to move up and down relative to the housing 12 and other pump components, including portions of the manifold assembly 58.

There are several interfaces associated with the rod 36 and other pump components which may become wear points as the flexible bladder 14, and in turn the rod 36, move upward and downward. Each interface requires bushings and/or other mechanical pieces to allow movement of the rod 36 relative to the other components of the pump 10. In addition, the break-in period for a new pump 10 employing the rod 36 as an indicator can be long, requiring careful initial filling of the pump chambers, and often leading to problems such as the flexible bladder 14 becoming wrapped around the rod 36.

Accordingly, and as shown in FIG. 3, one embodiment of the present invention provides a pump assembly 100 having certain components shown in FIGS. 1 and 2. Rod 36 is not present, and instead a flexible cable 136 is shown. Cable 136 extends through the manifold assembly 58 and can connect to the upper segment 32 of the bumper 30, as shown.

As shown, cable 136 can act as a position indicator for the flexible bladder 14 with surprising and unexpected advantages over the rod 36. Unlike the rod 36 which has a diameter of about 1.375 inches, the cable 136 has a significantly smaller diameter. In certain embodiments, the diameter of the cable 136 is about ⅛ of an inch. In other embodiments, the diameter of the cable 136 is about 1/16 of an inch. Unlike the rod 36, cable 136 is flexible, such that spooling the cable 136 instead of retracting the rod 36 away from the housing 12 results in occupying less space, for example in manifold assembly 58.

Because the cable 136 is smaller in diameter and is flexible, in certain embodiments, the cable 136 does not require as many components and interfaces subject to wear and tear as the rod 36 in the prior art embodiment. In certain embodiments, the use of the cable 136 allows less interface stack-up and less manufacturing tolerances because interfaces between bushings and the housing 12, interfaces between bushing and the rod 36, and/or interfaces between the housing 12 and sensors do not require fine control. In certain embodiments, lubrication around the interfaces is no longer required. Accordingly, the pump assembly 100 has a longer operating life. Furthermore, the flexible bladder is less likely to wrap around the cable 136, and the cable 136 will be less sensitive to operator error during flexible bladder break-in, pump chamber filling, and pressure testing.

As shown, cable 136 is coaxial with and extends through the manifold assembly 58 and can connect to the upper segment 32 of the bumper 30. However, in other embodiments, cable 136 can be in communication with other components of the flexible bladder 14 and will be displaced responsive to the movement of the bumper 30 and/or other components moving in pump housing 12 in response to fluid flow. Cable 136, in other embodiments, need not be coaxial with the manifold assembly 58, and more than one cable can be used, in some embodiments, to detect certain displacements of components in hollow pump housing 12 in response to fluid flow. In certain embodiments, a linear variable displacement transducer (LVDT) can be attached to the cable 136. Using a greater-accuracy, smaller range-of-motion transducer, for example a LVDT, enhances the accuracy of position measurement.

Experiment for Wire Linear Sensor

The following describes a successful endurance test of a CPI SL1200-506 linear sensor produced by CPI Control Products, Inc. of East Hanover, N.J. The CPI SL1200-506 linear sensor operated successfully for one million full-stroke cycles in a circulating salt water test tank. At the conclusion of testing, the test unit was functioning correctly. The unit was removed and disassembled for inspection and analysis. The concentration of the salt water was 35 grams of salt per liter of water. End-stop measurements were taken to determine the linear sensor's initial functionality over 25 inch strokes prior to submerging the sensor in salt water and just after submerging the sensor in salt water. The operating stroke length of the linear sensor was approximately 25 inches. Stroke distances during the test were slightly variable due to small variations in operating points of magnetic limit switches affixed to the pneumatic actuator.

Referring now to FIG. 4, a graphic representation of the linear sensor used in the presently described experiment is shown. The sensor had a resolution of 0.0027 inches per millivolt (0.068 mm per millivolt) (26.6 inches total range/10.00 volts). The maximum variation in the fully-extended data was about 72 millivolts. This corresponds to an error of about 0.194 inches maximum over one million cycles. The maximum variation in the fully-retracted data was about 245 millivolts. This corresponds to a maximum error of about 0.66 inches over one million cycles. Linear sensor 400 includes a sensor housing 402, sensor enclosure panels 404, a sensor body 406 disposed between the sensor housing 402 and a sensor conduit 408, a transducer cable 410 axially-aligned with and disposed in the sensor conduit 408, and a ferrule connector 412.

Sensor housing 402 further includes a spool assembly 414 and guide rollers 416 for transducer cable 410. In embodiments of the present disclosure, ferrule connector 412 can be removeably connected to upper segment 32 of the bumper 30, and as water space 18 is filled, transducer cable 410 would be pulled out of sensor conduit 408 allowing for detection of displacement of the linear sensor 400. Alternatively, as mud space 16 is filled applying pressure to flexible bladder 14, transducer cable 410 would retract into sensor conduit 408 and sensor housing 402 allowing for detection of displacement of the linear sensor 400.

In certain embodiments, the sensor housing 402 includes an internal pre-tensioned coil spring (not shown), where the coil spring causes the cable 410 to always be in tension. The tension is not strong enough to physically cause the flexible bladder 14 to move. However, when the bladder is caused to move, either towards the mud space 16 or towards the water space 18, in response to the water space 18 being filled or the mud space 16 being filled, respectively, tension in the wire is sufficient to both allow the cable to extend (as the bladder moves toward mud space 16) and cause the cable 410 to retract quickly enough, preventing the cable 410 from having slack (as the bladder moves toward the water space 18).

During testing, an end loop on transducer cable 410 was redesigned to include ferrule connector 412 to avoid wear and breakage of the cable. FIG. 5 shows an enlarged view of ferrule connector 412. As shown, ferrule connector 412 includes threads 418 and cable connector 420.

The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise.

In the drawings and specification, there have been disclosed embodiments of methods and systems for detecting the position of a pump bladder within a pump housing, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The embodiments have been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the present disclosure as described in the foregoing specification, and such modifications and changes are to be considered equivalents and part of this disclosure. 

What is claimed is:
 1. A pump with a position indicator, the pump comprising: a pump housing, wherein the pump housing includes a flexible bladder disposed therein; a first fluid zone, wherein the first fluid zone is operable to allow flow of a first fluid into and out of the first fluid zone; a second fluid zone, wherein the second fluid zone is operable to allow flow of a second fluid into and out of the second fluid zone; and a flexible position indicator disposed in the first fluid zone and in communication with the flexible bladder, wherein the flexible position indicator is operable to detect a linear position of the flexible bladder, and wherein the flexible bladder fluidly isolates the first fluid zone from the second fluid zone.
 2. The pump according to claim 1, wherein the flexible position indicator comprises a transducer cable.
 3. The pump according to claim 2, wherein the flexible bladder is operable to move toward the second fluid zone when the first fluid flows into the first fluid zone, wherein the flexible bladder is operable to move toward the first fluid zone when the second fluid flows into the second fluid zone, and wherein the flexible position indicator is attached to the flexible bladder and is displaced according to motion of the flexible bladder.
 4. The pump according to claim 2, further comprising a sensor housing with a spool assembly and guide rollers to store and guide the transducer cable, wherein the transducer cable extends from and retracts into the sensor housing in response to tension, and not in response to compression.
 5. The pump according to claim 2, wherein the transducer cable comprises a ferrule connector and the flexible bladder comprises a bumper, and wherein the ferrule connector is attached to the bumper.
 6. The pump according to claim 1, wherein the pump further comprises a linear variable displacement transducer (LVDT).
 7. The pump according to claim 1, wherein the first fluid comprises seawater and the second fluid comprises drilling mud.
 8. A dual gradient drilling system for subsea operations, the drilling system comprising: a water supply line comprising a water supply line inlet and a water supply line outlet; a manifold inlet, the manifold inlet in fluid communication with the water supply line; a mud return line comprising a mud return line inlet and a mud return line outlet; a mud lead line, the mud lead line in fluid communication with the mud return line; a pump housing, wherein the pump housing includes a flexible bladder disposed therein, wherein the flexible bladder fluidly isolates the manifold inlet from the mud lead line; and a flexible position indicator disposed proximate the manifold inlet and in communication with the flexible bladder, wherein the flexible position indicator is operable to detect a linear position of the flexible bladder within the pump housing.
 9. The drilling system according to claim 8, wherein the flexible position indicator comprises a transducer cable.
 10. The drilling system according to claim 9, wherein the flexible bladder is operable to move toward the mud lead line when water flows into the manifold inlet, wherein the flexible bladder is operable to move toward the manifold inlet when mud flows into the mud lead line, and wherein the flexible position indicator is attached to the flexible bladder and is displaced according to the motion of the flexible bladder.
 11. The drilling system according to claim 9, further comprising a sensor housing with a spool assembly and guide rollers to store and guide the transducer cable, wherein the transducer cable extends from and retracts into the sensor housing in response to tension, and not in response to compression.
 12. The drilling system according to claim 9, wherein the transducer cable comprises a ferrule connector and the flexible bladder comprises a bumper, and wherein the ferrule connector is attached to the bumper.
 13. The drilling system according to claim 8, wherein the system further comprises a linear variable displacement transducer (LVDT).
 14. The drilling system according to claim 8, wherein the water supply line comprises seawater and the mud return line comprises drilling mud.
 15. A method for detecting displacement of a displaceable component in a pump housing, the method comprising the steps of: disposing a flexible position indicator proximate the pump housing and in communication with the displaceable component in the pump housing, the displaceable component operable to be displaced by fluid movement in the pump housing; allowing the flexible position indicator to be displaced responsive to movement of the displaceable component in the pump housing; detecting a displacement of the flexible position indicator; and monitoring a position of the displaceable component in the pump housing.
 16. The method according to claim 15, wherein the pump housing includes a flexible bladder disposed therein.
 17. The method according to claim 15, wherein the flexible position indicator comprises a transducer cable.
 18. The method according to claim 17, wherein the step of allowing the flexible position indicator to be displaced responsive to the movement of the displaceable component in the pump housing occurs in response to tension on the transducer cable, and not in response to compression.
 19. The method according to claim 15, wherein the pump housing further comprises a linear variable displacement transducer (LVDT).
 20. The method according to claim 15, wherein the fluid movement in the pump housing comprises movement of at least two different fluids in two fluidly isolated chambers of the pump housing. 